1. Field of the Invention
The present invention relates to a magnetic-force generating apparatus for generating magnetic force for levitating a transport vehicle adopting a magnetic levitation system off the surface of a rail.
2. Description of the Prior Art
In general, a transport vehicle employing a linear motor system and a magnetic levitation system is levitated off the surface of a rail fixed on a track girder by means of magnetic force generated by a magnetic-force generating apparatus installed on a body of the transport vehicle. The magnetic-force generating apparatus comprises a plurality of electromagnets. The transport vehicle is moved by means of a thrust force generated by linear motor including a metal plate fixed on the track girder or the rail and a field magnet body of a linear motor installed on the body of the transport vehicle.
A plurality of truck bodies are installed on the lower portion of the body of the transport vehicle on both sides of the body with respect to the moving direction of the transport vehicle and in parallel with said moving direction. Each truck body is equipped with a levitation-magnetic-force generating apparatus comprising a plurality of electromagnets. The number of electromagnets included in a levitation-magnetic-force generating apparatus is usually a multiple of two. The electromagnets are arranged to line in a row in the moving direction of the transport vehicle. In the case of a transport vehicle adopting a normal-conducting magnetic levitation system, the levitation-magnetic-force generating apparatus generates magnetic force that serves as an attraction for levitating the transport vehicle off the surface of the rail.
While the transport vehicle is travelling along the rails, the levitation-magnetic-force generating apparatus generates magnetic force for guiding the apparatus to travel along the rails smoothly, and at the same time, for preventing pitching of the vehicle, that is tilting movement of the vehicle body in the longitudinal direction thereof and inclination and movement of the vehicle body in the transverse direction thereof as well. It should be noted that the magnitude of the magnetic force generated by the levitation-magnetic-force generating apparatus for levitating the body of the transport vehicle off the surface of the rail is usually determined so as to levitate the interfacing surfaces of the cores of the electromagnets generating the magnetic force away from the top surface of the rail by a gap of the order of 6 to 10 mm. In spite of the fact that such a small gap is to be sustained, there are variations in manufacturing precision of the electromagnets and variations in installment accuracy of the electromagnets on the truck body. Accordingly, while the transport vehicle is travelling, the cores of the electromagnets fixed on the levitation-magnetic-force generating apparatus may come into contact with the rail or joints of the rail.